Electrical furnace.



H. NATHUSIUS.

v ELECTRICAL FURNACE. APPLICATION Flu-:D ocr. s. 1914. BENI-:WED MAR. so, 19m

1 ,265,485 .Patented Ma 1918.

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` javax/W1 ffmfm 1 W @wia 1 Ww H. NATHUSIUS.

ELECTRICAL FURvNACE. APPLlcATIoN FILED oc. 5, Ism. Eril-:WED MAR. so. 191s.

A 1,265,485. Patend May 7,1918.

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HANS NATHUSIUS, 0F FIBiIEDENSHTTE, KREIS BEUTHEN, GERMANY.

ELECTRIGAL FURNACE.

Specification of Letters Patent Patented May 7, 1918.

IApplication led October 5, 1914, Serial No. 865,057. Renewed March 30, 1918. Serial No. 225,850. y

To all whom z't may concern.'

Be it known that I, HANS NATHUsrUs, a citizen of the German Empire, residing at Friedenshtte, Kreis Beuthen, Germany, have invented certain new and useful Improvements in Electrical Furnaces, of which the followin is a specification.

My invention relates to improvements in electrical furnaces, and more particularly in furnaces which are heated by t-he resistance offered to the electric current passing through the lining of the wall of the furnace and through the charge, and which are closed all around in an air tight manner, which is possible because heating by means of arcs bydisplaceable electrodes is avoided. Furnaces of this class are designed for example for carrying out metallurgical processes, for example for obtaining zinc. A furnace of this class forms the subject matter of my copending application Ser. Nr. 812,209, filed January 15th, 1914s.A My present invention relates'to an improvement of the furnace described in this application.

In the furnace described in the said a plication the electrodes which provide t e terminals of the multipliase system are disosed in pairs on opposite sides of the chamer of the furnace, and there is a potential difference between all the electrodes. The electrodes are so connected to the supply circuit that between pairs of oppositely arranged electrodes there is the maximum potential difference, z'. e. the non-interlinked phase voltage, which corresponds to the maximum resistance between the said electrodes. 'However, bet-Ween electrodes which are immediately adjacent to each other there is 'a potential difference of' which is higher than the potential difference between two electrodes which are obliquely opposite to each other,-and which are ata greater distance away from each other, the potential difference between these electrodes being only 0.5 Ep. Therefore there is no uniform flow of current between the electrodes', and the heating effect between adjacent electrodes is higher than between electrodes which are obliquely opposite each other.

The object of the improvements is to dispose the electrodes in such a way, that the current and the heating effect are uniform throughout the heating chamber. With this object in view my invention consists 'in diselectrodes correspond to the distances thereof and the resistances between the same. 'I hereby the heating effect on the charge and lining of the furnace is perfectly uniform. The invention can be carried out in different ways. In one embodiment the electrodes are parallel to the longitudinal axis of the furnace and extend from one end to the other of the chamber, in which case the'potential dlfferences between the electrodes are proportional to the relative distances of and the reslstances between the same.`

If the furnace is not uniformly charged, or the conductivity of the charge is not uniform 1n all the zones, it may happen, that the current does not flow through the chamber uniformly over the whole length of the same. In order that also in such cases the How of the current through the charge be uniform, the secondary windings of a transformer for multiphase or threephase current are subdivided into sectional windings and connected with electrodes which in each phase series are arranged in star connection or circumferentially around the heating chamber in such a way, that not only the o-` tential difference between the pairs of e ectrodes corresponds to the distance of and the resistance between the electrodes, but that also between adjacent sets of electrodes there is the proper potential difference, so that the current must necessaril be uniform between adjacent sets of electro es. B thus arranging the electrodes I am enab ed to adapt the current fiowing between 'the electrodes of one or more series of phases to different conditions by regulating the current supply t'o the series of phases by means of potential regulation. The construction is further preferable for the reason,` that comparatively short electrodes are used, so that the walls of the furnace are not destroyed by expansion of the electrodes being heated, as is the case where long electrodes are provided.

For the purpose of explaining the invention an example embodying the same has been shown in the accompanyin drawings, in which the same letters of re erence have been used in all the views to indicate corresponding parts. ln said drawings- Figure 1, is a longitudinal section of the furnace taken on the line 1-1 of Fig. 2,

Fig. 2, is a cross-section of the furnace taken on the line 2 2 of Fig. 1 and showing the position of the electrodes,

Fig. 2a, is a diagram illustrating the How of the currents and the potential diderences between the electrodes,

Fig. 3, is a diagrammatical view illustrating a modification of the furnace, and

Fig. 4, is a longitudinal section through the furnace according to Fig. 3. For clearness sake the sets of electrodes are shown as being disposed in the same planes. l wish it to be understood that the invention is not limited to the number of electrodes shown in the figures, and that any desired number of sets of electrodes can be provided. ln all the casesv the electrical connection is alike in principle, and the number of the sections of the 4 secondary of the transformer corresponds to. the number of the sets of electrodes, or a corresponding multiphase'current is supplied to the electrodes.

Referring to the example illustrated in Figs. 1, 2, and 2, the chamber A of the furnace is closed all around, the electrodes do not project into the heating chamber and are covered by a lining having a suitable electrical resistance.

ln some cases, for example, where the ends of the electrodes are not liable to be destroyed by melting or destruction by the charge or by the chemical agents produced in the process, and the charge can not be made impure by the electrodes, the electrodes can project into the melting chamber.

In the example shown in Figs. 1, 2, and 21 six electrodes E are uniformly distributed around the circumference of the heating chamber, and the electrodes are, disposed in pairs diametrically opposite each other and connected to the source of electric current. As appears from Fig. 1 the current Hows through the apparatus in the following Way: If E79 is the phase voltage, the potential difference between opposite electrodes E, .and El', E2 and E2', and E3 and E3 is always Ep, and the potential differences of the other electrodes appear from the following table:

As appears from Fig. 1, the electrodes extend over the whole length of the chamber A which is connected in the usual way with one or more receivers or condensers B.

Vhere electrodes of considerable length are objectionable, similar electrical connections can be used in connection with sixphase current or three-phase current with the proper subdivision of the secondaries and with several sets of electrodes located one behind the other, as is shown in Figs. 3 and 4. The electrodes which have been indicated by the numerals 1, 2, 3, 1, 2', 3 correspond as to their position and arrangement to the electrodes of the furnace shown in Figs. 1, 2 and 2a to which corresponding letters have been applied. Below the 'said electrodes` there is a corresponding set of electrodes l, Il, lill, l', H', lill', which are likewise connected to the secondaries of their transformer in such'a way, that between opposite electrodes l and l', lll and ll', and lll and lill there is the full phase voltage, while between the other pairs of electrodes there are the following potential dierences:

Apart from this there is a potential difference between the electrodes of 'one set and the electrodes of the other set, so that the charge is traversed by heating currents of uniform intensity and, apart from this, is surrounded by a uniform net of current lines which traverse the lining covering the ends of the electrodes so as to heat the same.

rlhe supply of electric energy to the individual sets of electrodes or series of phases can be automatically controlled by suitable 4means such as potential regulators.

rent connected with said electrodes in such a way, that the potential differences between any of the electrodes correspond to the distanceand the resistance between such electrodes.

2. A closed electric furnace having a heating. or reducing chamber whose walls are composed of electrically resistant material which is electrically conductive when heated said walls having iixedly embedded in an.

air tight manner outside of the chamber a plurality of annular disposed sets of electrodes disposed symmetrically at the circumference of the chamber parallel to its axis and a source of multiphase current connected with said electrodes in such a way that the potential differences between any of the electrodes correspond to the distance and the resistance between such electrodes and that there is also potential difference between the adjacent sets of electrodes.

composed of electrically resistant material" which is electrically conductive when heated, said walls having xedly embedded in an air tight manner outside of the chamber av plurality of annular disposedsets of electrodes disposed symmetrically at the circumference of the chamber parallel to its axis, said annular sets of electrodes being connected with as much subdivisions of the secondary windings of a source of multiphase current as there are annular sets of electrodes in such a way that the potential differences between any of the electrodes correspond to the distance and Ithe resistance between such electrodes and that therel is also potential difference between the adjacent sets of electrodes.

In testimony whereof I alix my signature in presence of two witnesses.

DR. ING. HANS NATHUSIUS.

Witnesses:

HUGO JANUSZEWSKI,

HERBERT SCHILLER. 

